CVE-2026-126063

Nokogiri is an open source XML and HTML library for the Ruby programming language. From 1.12.0 until 1.19.5, the C extension on CRuby and TruffleRuby has a Nokogiri::HTML5 serializer that does not escape text inside noscript elements or angle brackets inside attribute values. When an application sanitizes untrusted HTML with the default parsing options, allows noscript, and sends serialized output to a scripting-enabled browser, the browser can parse markup that Nokogiri did not produce, enabling mutation cross-site scripting. Using parse_noscript_content_as_text: true is the recommended workaround, not the vulnerable default. JRuby is not affected because it does not implement Nokogiri::HTML5. This issue is fixed in version 1.19.5.

• CWE-79
• CWE-116

• https://github.com/sparklemotion/nokogiri/commit/3e84df6ff7ab4d78f446e3a415430bd69a055d32
• https://github.com/sparklemotion/nokogiri/commit/c6c0bffbdcd194694995acafeeed27326b0805f8
• https://github.com/sparklemotion/nokogiri/pull/3752
• https://github.com/sparklemotion/nokogiri/releases/tag/v1.19.5
• https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-4p39-36wj-23h4

Published

Nov 10, 2026

Last Modified

Nov 12, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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